1. Field of the Invention
This invention pertains generally to circuit interrupters and, more particularly, to such circuit interrupters employing one or more pole mechanisms.
2. Background Information
Circuit interrupters provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits and abnormal level voltage conditions. Typically, circuit interrupters include a spring powered operating mechanism which opens electrical contacts to interrupt the current through the conductors of an electrical system in response to abnormal conditions.
Circuit interrupters, such as, for example, power circuit breakers for systems operating above about 1,000 volts typically utilize vacuum interrupters as the switching devices. For the higher voltages, or for a more compact arrangement, each vacuum interrupter is housed in a separate pod molded of an electrically insulative material, such as a polyglass. These molded pods, in turn, are bolted to a metal box containing the operating mechanism. The metal box is grounded to isolate the operating mechanism from the line voltage of the power circuit. Manual controls for the operating mechanism are accessible at the front face of the metal box. See, for example, U.S. Pat. No. 6,373,358.
Vacuum circuit interrupter apparatus include separable main contacts disposed within an insulating housing. Generally, one of the contacts is fixed relative to both the housing and to an external electrical conductor which is interconnected with the circuit to be controlled by the circuit interrupter. The other contact is moveable. In the case of a vacuum circuit interrupter, the moveable contact assembly usually comprises a stem of circular cross-section having the contact at one end enclosed within a vacuum chamber and a driving mechanism at the other end which is external to the vacuum chamber. An operating rod assembly comprising a push rod, which is fastened to the end of the stem opposite the moveable contact, and a driving mechanism provide the motive force to move the moveable contact into or out of engagement with the fixed contact.
The operating rod assembly is operatively connected to a latchable operating mechanism which is responsive to an abnormal current condition. When an abnormal condition is reached, the latchable operating mechanism becomes unlatched which causes the operating rod to move to the open position. The motion of the operating rod, in turn, causes a contact bell crank to rotate and this controls motion of the moveable contact.
Compression springs are provided in connection with the operating rod assembly in order to be able to separate the moveable contact from the fixed contact and to assure the necessary force so that the contacts will not accidentally open under inappropriate conditions. In addition, when appropriate circumstances requiring interruption of the circuit do arise, an adequate force is needed to open the contacts with sufficient speed. If the contacts do not open quickly, then there is a risk of the contacts welding together and failure to interrupt the current.
Vacuum interrupters are typically used, for instance, to reliably interrupt medium voltage alternating current (AC) currents and, also, high voltage AC currents of several thousands of amperes or more. Typically, one vacuum interrupter is provided for each phase of a multi-phase circuit and the vacuum interrupters for the several phases are actuated simultaneously by a common latchable operating mechanism.
U.S. Patent Application Publication No. 2004/0118815 discloses an electrical interrupter apparatus including an interruption device, an insulation member, a base, a driving system and a linkage mechanism. A plurality of the electrical interrupter apparatuses may be incorporated into a circuit breaker, such as a 72.5 kV outdoor circuit breaker or other circuit breaker. The driving system includes a drive unit and a return spring. The drive unit is mounted within the base and can be any of a wide variety of mechanical devices suited to rapidly provide a sufficient level of force at a sufficient speed to operate the interruption device in an appropriate fashion. The drive unit may be of a variety of different configurations, and may be, for instance, a motor, a solenoid, a permanent magnet linear actuator, or other appropriate device.
U.S. Pat. No. 6,362,445 discloses a breaker module comprising a vacuum interrupter/linear actuator assembly. The vacuum interrupter portion of the breaker module is a conventional circuit breaker vacuum interrupter design including a moveable contact stem/push rod assembly that is connected to the armature of an in-line actuator, which drives the moveable contact into or out of engagement with a stationary contact in response to an input of an appropriate drive signal. The in-line actuator is of conventional design and consists of either one or two electrically wound coils wound around a magnetically permeable, hollow form positioned adjacent a hollow rare earth magnet. In the single coil design, voltage of a given polarity is applied to the coil to move the armature in a first direction and voltage of the opposite polarity is applied to the coil to move the armature in the opposite direction. In the two coil design, the magnet is interposed between the two coils and the armature is disposed in the hollow center. Voltage is applied to the first coil in a first direction to cause movement of the armature in one direction and voltage is applied to the second coil in the opposite direction to cause opposite movement of the armature.
In the event of a loss of power or other failure, there is a need to permit an operator to manually open the vacuum interrupter.
There is also a need for manual operation that is safe and reliable.
Accordingly, there is room for improvement in vacuum circuit interrupters employing an actuator.